The present technology relates to solid-state imaging devices, methods for manufacturing the same, and electronic apparatuses, and more specifically to a solid-state imaging device, a method for manufacturing the same, and an electronic apparatus in which a high-concentration impurity region can be formed in a semiconductor substrate and on the back side of the semiconductor substrate.
In general, charge coupled device (CCD) and complementary metal oxide semiconductor (CMOS) image sensors of the related art have a configuration in which pixels of colors of green, red, and blue are arranged on a plane and a photoelectric conversion signal of green, red, or blue is obtained from each pixel. Examples of patterns of green, red, and blue pixels include a Bayer pattern of pixels in blocks of four pixels having two green pixels, one red pixel, and one blue pixel.
In the CCD and CMOS image sensors of the related art, therefore, a single-color signal is obtained from each pixel. Thus, it is necessary to perform signal processing called demosaicing processing on, for example, a green pixel to interpolate blue and red signals from signals of the adjacent blue and red pixels. However, such signal processing leads to a degradation in image quality called false color. In order to prevent the degradation in image quality caused by false color, it is desirable that three photoelectric conversion layers be stacked vertically on top of one another so that photoelectric conversion signals of three colors may be obtained from one pixel.
Therefore, an image sensor is available in which, for example, photoelectric conversion films of green, red, and blue are stacked on top of one another on a semiconductor substrate so that photoelectric conversion signals of green, red, and blue can be obtained with one pixel (see, for example, Japanese Unexamined Patent Application Publication No. 2006-222278).
There is another image sensor in which a photoelectric conversion film of one color (green) is formed on a semiconductor substrate and photoelectric conversion units of two colors (blue, red) are formed in a semiconductor layer so that photoelectric conversion signals of green, red, and blue can be obtained with one pixel (see, for example, Japanese Unexamined Patent Application Publication No. 2006-278446).
The technologies described above provide a structure in which photoelectric conversion layers are stacked on top of one another on a front surface of a semiconductor substrate on which wiring is formed (“front-illuminated multilayer image sensor”), and have a feature in that signal charges in the stacked photoelectric conversion layers are temporarily accumulated in the semiconductor layer. If light enters a semiconductor region where the signal charges obtained in the stacked photoelectric conversion layers are accumulated, signals having components other than the components in the photoelectric conversion layers may be contained in photoelectric conversion signals in the semiconductor region, and color mixture may occur. In such a stacked image sensor as above, therefore, it is necessary to form a light-shielding layer to prevent light from leaking in the semiconductor region where signals from the stacked photoelectric conversions are accumulated.
In the front-illuminated multilayer image sensor described above, however, it is difficult to realize a light-shielding layer. Therefore, a back-illuminated image sensor having a structure in which a photoelectric conversion layer for one color which is formed of an organic photoelectric conversion film is stacked on a semiconductor substrate and photoelectric conversion layers for two colors are stacked on top of each other in the semiconductor substrate has been proposed by the present assignee (see, for example, Japanese Unexamined Patent Application Publication No. 2011-29337). In this structure, it is necessary to form a high-concentration impurity region near the interface of the semiconductor substrate and on the back side of the semiconductor substrate to obtain ohmic contact with a contact plug for extracting signal charges from the organic photoelectric conversion film.